Biplanar ophthalmic lens die



July 4, 1939. H. A. couRMETTEs BIPLANAR OPHTHALMIC LENS DIE Filed June24, 1938 pvenlar.

Patented July 4, 1939 UNITED. STATES PATENT OFFICE BIPLANAR OPHTHALDHGLENS DIE Henry A. Courmettes, Brooklyn, N. Y.

Application June 24, 1938, Serial No. 215,646

4'Claims. (Cl. ESL-216) My invention relates primarily to thesurfacsketched herein and explained below, extending of the outersurfaces of biplanar ophthalmic ing and adapting it to the process ofcomputing lenses such as described in U. S. Patent and measuring angularsurfaces of dies for oph- #1,991,544. The difficulties in grinding thesethalmic lenses, I produce a most practical and surfaces correctly in theorthodox single lens accurate method for surfacing the outer surfaces 5process, brought about by the necessity of inof biplanar lenses.dividual calculations for lens thicknesses at vari- I state thisprinciple thus: ous points of their-edges, and the correct cen- When twocircles, having different diameters, tering of pivotal centers of lensblocks to which one exactly twice that of the other, are placed thelenses are secured, have been overcome by together with the smallerentirely contained my new lens dies which simplify the surfacing withinthe larger, tangent to it on one side and operation and result inprecise and rapid work. intersecting, its center of radius on the other,

To more completely understand the function a straight line drawn fromthe point of tangency r of these lens dies, I am describing thegeometric of the two circles to any other point on the r 10 principlewhich brought their conception, the aplarger circle is bisected atexactly one half of plication of the principle to their construction,its length by the smaller circle. the description of their use, therules for lens The following terms are used to name the and gaugecomputations, formulas etc. various optical factors and wherein thecurva- References are made to the drawing which tures and powers areexpressed in dioptric values:

forms a part of the invention and in which: Dizouter Surface curvature 0F g. 1 s a drawing of the geometric principle. Dzzinner surfacecurvature Fig. 2 1s a drawing of the geometnc principle Dszcurvature ofgauge for measuring angular extended to show its application toophthalmic form of dies lens dies.

R=Ra 0 er of lens. Fig. 3 is a face View of the lens die showingtzthicklzlegs of glass in millimeters 25 its two surfaces and a form ofedges correspondnzrefmction index of glass mg to the are shape of thenear Vision portion O=center point of gauge contact at center line ofthe lenses and used in their grinding. of die v 1S face w of the lens(he showmg Xl=outer point of gauge contact, arched edg its two surfacesand a form of edges correspondline of die 30 ing to the arc shape of thedistant vision porxzzouter point of gauge Contact juxtaposed tion of thelenses and used in their grinding. to XI Fig. 5 is a face view of thetesting gauge and X 0ptia1 axes a sectional side view of the die, incombination, I showing the application of the testing process Wh theseterms are applled t0 the em' etr 35 by the three point contact ofdie tothe curvature pllnclple 0n E. then, of ggt D|=the curvature of the largecircle.

6 a sectlonajl D2=the straight line, or co-linear-chords of both Fig. '71S a back side view of Figs. 4 and 6. circles. Fig. 8 is a sectionalside view of two lenses D3zthe curvature fth small e '40 in position ona lens die, in the process of surfacing their continuous outer surfaces,clearly and @1115 sketchproves the prmclple y Showmg showing opticaleffects obtained by curves, angles D2 blsected at exactly one half ofIts length and abutting edges. by

5 Fig. 9 is a face view of Fig. 8in position for Q extfendmg theprmclple to t shown surfacing the lower, or near vision, portion of mWhlch 15 actually a-doublmg of the t 1911565, original principle, Iobtain the condition mainly Fig. 10 is a face view of a biplanar lensshowused in y methods. namely; a three po nt ea ing its curved line ofdemarcation across its uring process for dies and gauges. In this socenter. sketch, by using-the same'point 'of tangency 0," 56

Fig. 11 is a sectional side view of Fig. 10 showthe two straight linesD2 are seen to be at an ing the angle at the line of demarcation usedangle to eachother and bisected at O, XI, X2 to rest against the guidingcurved edges'of the by the circle D3. dies. I Assuming that the twolines D2 represent the Beginning with the geometric principleinner-surfaces-of two plane-convex optical lenses- 5 5"" while in theangular position shown in Fig. 2, a continuous curve DI, with a commoncenter, could be surfaced over both lenses which would then representtheir outside surfaces; the optical axes X traversing the lenses at XIand X2, as shown, would correspond with the centers of the lines D2 andthe geometric center of each lens. Assuming, further, that the lensesare supported by a solid holder extending from XI to X2 in length andplaced against thelines D2 with its two surfaces inclinedtofollowtheangular form XI to O and 0' to X2, then, a form for this saidholder, herein also called die, would be obtained whereby its edges atXI and X2 and its center at 0 would lie on the curve of the small circleD3 the radius of which would simply be one half that of the outsidesurfaces DI. Y

It follows, then, that it becomes possible to obtain a controllableangle of diesurfaces and also a guide to control the position of thelenses on the die relative to thedesired location .of optical centersand from this evolves the process of making dies withfangular' races andof such contours to holdftwobiplanar 'lenses'in a relative positionduring'the surfacing operation; D3 then becomes the'indispensable'measuring tool. and from it depends the accuracy of the dies'to producethe lenses they are intended for.

I prefer to shape these dies as in Figs. 3, ,4, where their edges at XIand X2 correspond with the arc .shape of the dividing line of b-iplanarlenses and act as a perfect fitting guide for securing the lenses to thedie. The edges .XI, X2. of Fig. 3

conform to the biplanar lens arc of the lower portionof the lens andFig. 4 to that of the upper portion.

,I amv aware that other shapes of edges could accomplishthe same result,such as a triangular edge, etc., butthe perfect arc is by far the'bestfor'accura'cy, measuring ease, wear, protection of lens surfaces andother important'advantages As is understood from the above descriptions,

the process of measuring dies in'this method isarrived at by obtaining asimultaneous contact of the three points XI, 0', X2 withthe curve of thegauge intended' for them. This isdone directly on dies intended for'plu's power lenses and on matrix molds for minus lenses- The surfacesof these dies are ground, and smoothed to correspond with the lenssurface curvatures; this is im-- portant as unless a perfect and evencontact is made between them, the resultant would be incorrect. 7

Consideration must be given to lenses which i have other than fiat innersurfaces, thicknesses of lenses, powers, optical center, etc., thisinvolves computing thevarious factors entering each con dition, but themethod remains the sameffor all of thein." I V The following examplesare given as general rules to compute the various elements according totheir particular factors and to provide a method to obtainangularrelation of the surfaces, in the making of the dies, the inventionhowever is not confinedsolely tothe' method described but may ,use anymathematical or instrumental means and methods known. In Examples 1 and2 the optical centers ofthe lenses are calculated to coincidewith X LandX2, R represents the total R1: power inthe vertical-meridian, andt-equals the thickness of glassrequired by R13 poweritself; foralenshaving a diameter twice that'of die surface, i, e.,'XI to 0x 2. InExample 3, D3 is the re-,j

sultant combination of that found by Formulas 1 or 2 together withtheequation for-vertical deg then 2. If vertex effective power of Rx iswanted,

1523 being the index of glass and 1.530 the index of tools ordinarilyused in the manufacture of ophthalmic lenses, then the computationsbecome this:

L 'D3=D3-(% [D3+'D2] or I g V V V A D3+( X[D3+ according to therespective, up or down, direction of 'decentration and where,A=Decentration in m/m B =0 ne half diameterf individual surfaces of die.1

Lateral decentration" is measured hand;

calipers' as in theordinary single lens process,

'4. Where'the' thickness of plus lenses at O, or minus lenses, at XI X2is appreciable, the radius of D3 should be shortened by a similarlength.

Referring to the drawing, inFigs. 5, 8, 9, the

their two angular faces K to conform ,with the lens surface curvaturesD2 and at such angle to each other that, in line with the center of thedie, their edges XI, X2 and the center line of joinder Offorrn a threepoint simultaneous contact with the predetermined spherically curvededges D3.

of gaugeM, andlapping, or shaping, the edges XI, X2foffsaidfldies to fitthe are shaped inner demarcation line L of biplanar lenses E, andproviding the reverse side with suitable pivotal centers C, orconnections adaptable to surfacing,

mec a sm: rl s r Y I I prefer to make these dies with a hard but light mtal suc as dur lu niu for. tter. ease in v v I V (5) method of makingthe dies consists in lapping I,

working and handling, and the gauges, as ordinarily made, in brass.

I am aware that my lens dies may be made of varied shapes and incomposite form without changing their principle and effect, therefore Iam not confining my claims to the exact forms sketched but also toothers using my method of measuring and accomplishing the same result.

The word die has been used herein instead of holder, block, etc. commonin lens making, to befit the function and precision of the new devicewithout prejudice to its otherwise named useful applications.

I know that lens blocks have been made in various forms for multiplelens grinding, but I do not believe, the art of biplanar lenses beingnew, that a precise lens die made to hold two such lenses in a relativeangular position and at the same time fitting their are shaped dividingline has ever been made before my invention thereof, nor my method ofmeasuring them, therefore I claim as new:

1. A die for blocking ophthalmic lenses in the process of surfacegrinding comprising, on one side, two angularly disposed and lappedsurfaces evenly joined in a line at its center, two juxtaposed edgescurved to fit the inner line of demarcation in biplanar lens surfacesand. guide the positioning of said lenses upon the said die, whereby thecurved edges and the line of junction of the two surfaces at the centerof said die lie on a predetermined curve, and suitable pivotal centerson the opposite side of said die,

2. A die for blocking ophthalmic lenses in the process of surfacegrinding comprising, on one side, two angularly disposed and lappedsurfaces evenly joined in a line at its center, two juxtaposed edgesshaped to fit and abut against the inner line of demarcation in biplanarlens surfaces and guide the positioning of said lenses upon the saiddie, whereby the said edges and the line of junction of the two surfacesat the center of said die lie on a predetermined curve, and on itsopposite side, suitable form adaptable to surfacing mechanism.

, 3. A device to aid in surfacing the outer surfaces of biplanarophthalmic lenses consisting of a member formed to hold two such lensesin a stationary and predetermined relative angular position, to serve asfixed guide in positioning said lenses upon the said device by contactwith the inner line of demarcation in biplanar lens surfaces, to providethe feature whereby the said relative angular position may be measuredwith curvature gauges, and be adaptable to surfacing mechanism, as setforth.

4. A device to aid in finishing the outer surfaces of biplanarophthalmic lenses consisting of a solid member formed to include, on oneside thereof, features to hold two such lenses in a stationary andpredetermined relative angular position whereby in the surfacing processa desired form is imparted to said lenses controlling the angularrelation of their surfaces and location of their optical centers,features serving as fixed guides in positioning the said lenses upon thesaid device by contact with the inner line of demarcation in biplanarlens surfaces, and a feature whereby the said relative angular positionmay be measured with curvature measuring tools; on the reverse sidethereof, adaptability to surfacing mechanism in use.

HENRY A. COURNIETTES.

